1. Field of the Invention
The present invention is related primarily to an apparatus, method, and sealing device for repairing pipes and conduits, particularly high temperature, high pressure pipes and conduits, such as steam lines. More particularly, the invention is directed to an internal repair of a section of damaged, weakened, or leaking pipe or conduit, in which the section to be repaired is typically located in an inaccessible area, such as underground.
2. Background and Material Information
Conduit systems for conveying natural gas, water, and steam are typically located underground and, in general, are not easily accessible if repair or other maintenance is required after installation. Over a period of time, such conduit systems can become damaged, weakened, or can otherwise begin to leak, particularly at the joints between adjacent conduit sections, but also longitudinally along sections of the conduit. Thus, there can be a problem of ex-filtration of gas, water or steam from the damaged conduit sections.
Furthermore, in the repair of high temperature, high pressure pipes and conduits, such as steam lines, which are utilized by utility companies, there is usually a need to effect the repairs in as short a time period as possible. Thus, there is a need to effect high strength repairs to such high temperature, high pressure pipes and conduits quickly so that the utility lines can be returned to service in a relatively short period of time, such as less than one day.
Additional problems associated with similar systems, and a number of previous repair methods and apparatuses are disclosed, for example, in U.S. Pat. Nos. 5,119,862 and 5,351,720. These patents, which disclose "No-Dig" or non-excavation repairs, utilize a sleeve or liner which is transported to the site of the weakened or damaged pipe in a coiled or partially coiled configuration. Once the repair liner is located in the necessary position at the site of the repair, internal pressure is applied to the sleeve by means of an inflatable bladder or other means, which causes the sleeve to begin to uncoil and expand in the direction of the "host" pipe to be repaired. The sleeve, which includes a gasket or sealing compound on its outer surface, reaches a slight over-expanded condition, whereby the liner compresses the gasket or sealing compound against the inner surface of the host pipe. The internal pressure is then reduced or removed and the sleeve is slightly recoiled, whereby overlapping edges of the sleeve become locked in place by virtue of complementary locking devices.
The methods and apparatus disclosed in the aforementioned patents are intended primarily for the repair of conduits that carry wastewater and other fluids that are not in an over-pressure environment. However, a high temperature, high pressure pipe, such as a steam line, also requires periodic repair, particularly for sealing against ex-filtration, i.e., against a leak of the high temperature, high pressure fluid, such as steam, from the inside to the outside of the pipe.
The methods and apparatus disclosed in the aforementioned patents are useful for the repair of moderately high pressure pipes or conduits, although a particular problem, explained below, is posed. The size of these pipes is typically between 4 inches and 36 inches in diameter or even greater. Unlike an elastic compressible gasket or a polyurethane foam, e.g., which are usable for the repairs described in U.S. Pat. No. 5,351,720, high temperature, high pressure pipes and conduits may not be suitable for use with compressible gaskets, foam sealants, or epoxy resins or other curable, non-expansible sealants that are typically used in the prior art methods because the high temperatures and the moisture in the steam may degrade such sealants, breaking them down, and causing them to fail. Thus, the high temperature, high pressure fluid conveyed within the conduit may ex-filtrate through the degraded sealant, or the pressure of the fluid may cause the repair sleeve to fracture in the area of the repair which would also allow the fluid to ex-filtrate through the repaired section.